Detection of HIV is increasingly important given major advances in HIV treatment in recent years, yet among seropositive persons at least one-third of adults & 90 percent of adolescents are unaware of their serostatus. Variations in the organizational settings & contexts in which seropositive and at-risk persons may get tested appear to have a great influence on HIV testing, yet these contexts are rarely studied. Furthermore, the existing data come almost solely from public sector settings, which reflects only 10 percent of the HIV testing currently being conducted. To increase early detection of HIV, organizations must increase the percentage of clients offered testing who accept testing, the number of high-risk clients tested, the percentage tested who return for results, and the percentage of seropositive who are tested and linked to care. These outcomes should also lead to a reduction in time from infection to detection. This proposal examines the organizational factors (structures, processes, and intra- and inter-organizational relationships) that are likely to be associated with these outcomes in a two-phase project. In Phase I a qualitative study of these organizational factors will be conducted over 18 months in 5 major types of organizational settings that provide HIV testing in Los Angeles County: a publicly operated agency; a private non-profit organization; an HMO; a private, for-profit organization; and private practice offices. Multiple administrative and clinical staff in various roles within each organization will be surveyed in semi-structured interviews and self-report inventories, in addition to clinic observations and audits of existing records and polices. These data will be used to design and conduct a survey of a representative sample of organizational settings in LA County in Phase 2. Data will be collected on the HIV testing outcomes and organizational factors influencing the testing outcomes from 200 agencies within those five types of organizational settings in L.A. County. Within each agency, surveys will be conducted with various informants (n = 7-8 per agency), supplemented with clinical, administrative, and laboratory records. This survey will provide empirical data on the organizational structures, processes, intra- and inter-organizational relationships that influence early detection of HIV; this data will be used as the basis for developing and testing a future intervention on HIV testing organizations to improve their outcomes.